+
+
+
+## --------------------------------------------- ##
+## Defining C functions in both K&R and ANSI-C. ##
+## --------------------------------------------- ##
+
+
+# b4_modern_c
+# -----------
+# A predicate useful in #if to determine whether C is ancient or modern.
+#
+# If __STDC__ is defined, the compiler is modern. IBM xlc 7.0 when run
+# as 'cc' doesn't define __STDC__ (or __STDC_VERSION__) for pedantic
+# reasons, but it defines __C99__FUNC__ so check that as well.
+# Microsoft C normally doesn't define these macros, but it defines _MSC_VER.
+# Consider a C++ compiler to be modern if it defines __cplusplus.
+#
+m4_define([b4_c_modern],
+ [[(defined __STDC__ || defined __C99__FUNC__ \
+ || defined __cplusplus || defined _MSC_VER)]])
+
+# b4_c_function_def(NAME, RETURN-VALUE, [DECL1, NAME1], ...)
+# ----------------------------------------------------------
+# Declare the function NAME.
+m4_define([b4_c_function_def],
+[#if b4_c_modern
+b4_c_ansi_function_def($@)
+#else
+$2
+$1 (b4_c_knr_formal_names(m4_shiftn(2, $@)))
+b4_c_knr_formal_decls(m4_shiftn(2, $@))
+#endif[]dnl
+])
+
+
+# b4_c_ansi_function_def(NAME, RETURN-VALUE, [DECL1, NAME1], ...)
+# ---------------------------------------------------------------
+# Declare the function NAME in ANSI.
+m4_define([b4_c_ansi_function_def],
+[$2
+$1 (b4_c_ansi_formals(m4_shiftn(2, $@)))[]dnl
+])
+
+
+# b4_c_ansi_formals([DECL1, NAME1], ...)
+# --------------------------------------
+# Output the arguments ANSI-C definition.
+m4_define([b4_c_ansi_formals],
+[m4_case([$@],
+ [], [void],
+ [[]], [void],
+ [m4_map_sep([b4_c_ansi_formal], [, ], [$@])])])
+
+m4_define([b4_c_ansi_formal],
+[$1])
+
+
+# b4_c_knr_formal_names([DECL1, NAME1], ...)
+# ------------------------------------------
+# Output the argument names.
+m4_define([b4_c_knr_formal_names],
+[m4_map_sep([b4_c_knr_formal_name], [, ], [$@])])
+
+m4_define([b4_c_knr_formal_name],
+[$2])
+
+
+# b4_c_knr_formal_decls([DECL1, NAME1], ...)
+# ------------------------------------------
+# Output the K&R argument declarations.
+m4_define([b4_c_knr_formal_decls],
+[m4_map_sep([b4_c_knr_formal_decl],
+ [
+],
+ [$@])])
+
+m4_define([b4_c_knr_formal_decl],
+[ $1;])
+
+
+
+## ------------------------------------------------------------ ##
+## Declaring (prototyping) C functions in both K&R and ANSI-C. ##
+## ------------------------------------------------------------ ##
+
+
+# b4_c_function_decl(NAME, RETURN-VALUE, [DECL1, NAME1], ...)
+# -----------------------------------------------------------
+# Declare the function NAME.
+m4_define([b4_c_function_decl],
+[#if defined __STDC__ || defined __cplusplus
+b4_c_ansi_function_decl($@)
+#else
+$2 $1 ();
+#endif[]dnl